A major difficulty faced by owners of food delivery establishments is maintaining the temperature of hot foods, such as pizza, sandwiches, Chinese food, and the like, during delivery of the hot food from the kitchen to the customer. In colder climates, the difference in temperature between the heated food and the environmental temperature may be considerable, and thus result in significant cooling of the food, which may affect food quality, taste and safety during consumption.
Traditionally, pizza delivery establishments have addressed this problem by inserting the heated pizza into a box, usually formed from cardboard, and then into a receptacle or bag formed of thermal insulating material where the pizza would be kept during the delivery process. However, such thermal insulating pizza bags are limited in their ability to maintain the desired temperature by factors, such as delivery time and environmental temperature.
Still other heated food delivery systems utilize integrated electric energy heaters which require a relatively lengthy preheating period, e.g., up to two hours, before the food delivery container is available for the first heated delivery. As can be appreciated, a significant amount of energy and time is required to accomplish the foregoing, neither of which is conducive for fast food establishments, such as pizza restaurants. Also, in order to have an adequate amount of heated delivery containers ready during periods of peak delivery, the user would have to anticipate the number of heated delivery containers that would be needed and then commence the heating procedure well in advance of the actual use of the heated delivery container. Of course, if the user over estimates the number of heated delivery containers eventually required, costly energy is wasted in order to heat the unused containers. In the alternative, if the user underestimates the number eventually needed, the required lead/preheat time would preclude the user from obtaining a properly heated delivery container in the short time period required to satisfy today""s consumers.
In addition to the significant amount of energy and lead time required to preheat conventional food delivery containers, the space required by conventional pizza bag delivery systems is quite extensive due to peak period demand. For example, U.S. Pat. No. 4,816,646 to Solomon et al. discloses a typical conventional receptacle for maintaining the desired cooked temperature of food during delivery from the kitchen to the consumer. Solomon et al. utilizes a conventional electric resistance heater. FIG. 4 of the Solomon et al. patent illustrates a plurality of such receptacles mounted on shelves in a xe2x80x9creadyxe2x80x9d condition. Thus, in order to have an adequate number of heated delivery containers ready during peak demand, a substantial panel of the food establishment""s precious cooking space must be dedicated to preheating delivery bags.
Another deficiency of conventional heated food delivery containers, particularly pizza bags, is that they are designed to have a single food storage cavity for transporting the food product in a heated condition. Although many food establishments have attempted to accompany more than one food product into each container during peak demand, it results in inadequate interior temperatures within the container and, thus, reduces the quality of the transported food product. A need has arisen for an efficient bag which can carry more than one food container and yet maintain uniform heat throughout the bag so that one food product is not hotter than another.
Many conventional systems for heating conventional food delivery containers, such as pizza bags, rely on heating the food delivery container or a heating member which is then inserted into the food delivery container for a predetermined time period at a predetermined temperature. These conventional heating systems fail to provide a method for self-regulation of the heating system unless a regulator, like a thermostat, is added to the system. With such conventional heating systems, a food delivery container that has been heated, but has not cooled to ambient temperature, is still reheated during the subsequent heating cycle for the same predetermined time period as during the initial heating cycle. The use of such predetermined time period for subsequent heating cycles results in unnecessary expenditure of energy and time. Certainly, in today""s competitive business atmosphere both foregoing commodities must be utilized more efficiently than is provided by conventional food delivery containers, especially pizza delivery containers.
In addition to economy of time and energy, safety of the food service worker is a primary factor. As stated above, conventional food delivery containers, particularly pizza bags, rely on a predetermined time-period for heating the container. However, if the timer fails to deactivate the heating procedure, the temperature of the heating member will continue to rise. This result could not only destroy the food delivery container, but also creates a significant safety hazard to the food service personnel. The nature of the use of food delivery containers necessitates a great deal of actual handling by the food service worker under harried and hurried conditions. A need exists for a food delivery container that not only provides a shorter heating period, but also provides a fail-safe mechanism to prevent the container from over heating and still allow safe handling by the food service worker after the heating cycle.
A need continues to exist for a heated food delivery container that is able to maintain a heated storage area at an elevated temperature relative to ambient temperature, uniformly throughout the delivery container. A need also exists for a heat retentive delivery container that (1) utilizes less time to heat, (2) is self-regulating in its energy consumption during the heating process to require less energy and less time during subsequent heating cycles, and (3) has a fail-safe mechanism to prevent heating higher than a predetermined temperature. A need also continues to exist for a heated food delivery container that requires less preparation time and storage area than conventionally available heated delivery containers. An additional need exists for a system, which is capable of substantially reducing the lead time required to preheat a heated delivery container to its preferred transport temperature. A further need exists for a system which is self-regulating with respect to energy consumption and length of time of activation.
The present invention pertains to a storage container for maintaining food items at a desired temperature during transport thereof. More particularly, this invention pertains to food storage/delivery containers which include a novel self-regulating heat induction system which only heats the delivery container to a predetermined temperature regardless of the initial temperature of the delivery container when it is heated or reheated by the system. The present invention provides a novel induction-based heated delivery container system, which is capable of heating delivery containers in substantially less time than conventional electric heater or phase change technology. Due to the substantially reduced preheating time required, the container systems according to the present invention are capable of heating more containers per energy generation station than conventional systems, thus substantially reducing the amount of kitchen space required for preparation and temporary storage of the delivery containers. Additionally, the present invention provides a unique heating system, which is capable of self-regulation, i.e., brings each reused container back up to transport temperature without having to heat for a complete preheating cycle, i.e., starts at the current temperature of the container and only utilizes the required amount of energy to heat the container to its predetermined transport temperature. This greatly reduces preheating time, allows for rapid reuse of returned containers, and speeds up the entire delivery process. The present invention also provides a fail-safe mechanism to prevent the food service container from heating above a predetermined temperature. Finally, the novel heating system of the present invention allows for the transport of up to three separate pizza boxes per container without compromising food quality or transport temperature for each transported pizza contained therein.
A container for delivering heated food which comprises a receptacle formed from a substantially flexible material having at least one fail-safe heat storage member. The present invention also provides a novel self-regulating system and method for energizing such a container utilizing magnetic induction energy.
The self-regulating heat storage member comprises an inductive or magnetic material having a Curie-point and a heat storage material. (The terms xe2x80x9cinductive material,xe2x80x9d xe2x80x9cmagnetic materialxe2x80x9d and xe2x80x9cCurie point materialxe2x80x9d are used interchangeably herein.) The magnetic material is preferably nickel, chrome, iron, or mixtures thereof and with other trace materials present. The heat storage material is preferably aluminum. Use of aluminum for a heat storage member is a novel concept because aluminum is a heat dissipator. However, when aluminum is embedded within the fabric, it acts as a heat sink such that it stores heat in the fabric. The self-regulating heat storage member is preferably formed by casting or a combination of casting/cladding the heat storage member to the magnetic material. The aluminum acts as a heat sink and storage battery. The magnetic material preferably has a Curie point of between about 225xc2x0 F. to about 400xc2x0 F. It is preferable that the magnetic material contains holes and/or slits for the purpose of increasing attachment points to (1) increase the transfer of heat from the magnetic material to the heat storage material during the heating process, and (2) minimize possible detachment of the heat storage material from the magnetic material over time and use. As will be discussed below, the configuration of the holes and slits of the magnetic material that are xe2x80x9cfilledxe2x80x9d with aluminum provide a mechanism for compensating for and utilizing the different rates of expansion/contraction of the magnetic material versus the aluminum. The heat storage members for the present invention are approximately 8 to 8.5 inches in diameter and preferably 8.25 inches in diameter.
The present invention provides a system for heating food delivery containers which comprises: at least one container for delivering heated food which comprises a food compartment having at least one self-regulating heat storage member disposed therein, wherein the self-regulating heat storage member comprising a magnetic material; and at least one means for generating induction energy which is capable of heating the magnetic material to a predetermined temperature. In one embodiment of the invention, the system further comprises an automatic shut-off control which is capable of turning off the induction generating means when the magnetic material reaches the predetermined temperature.
The induction generating means comprises at least one means for generating a magnetic field disposed substantially in alignment with the heat storage member when the container is disposed adjacent to the induction generating means.
In one embodiment of the present invention, the container includes a compartment, wherein the compartment has an upper panel and a lower panel. The first self-regulating heat storage member has a magnetic material disposed within either the upper panel of the compartment or the lower panel of the compartment, the induction generating means comprises at least one means for generating a magnetic field disposed therein in such a manner that the magnetic material is in substantial alignment with the first magnetic field generating means, when the container is disposed adjacent to the induction generating means.
In a further embodiment of the invention, the self-regulating heat storage member further comprises a heat storage material in thermal contact with the magnetic material, wherein the heat storage material acts as a heat sink and storage battery. The magnetic material is selected from the group consisting of: nickel, chrome, iron and mixtures thereof. The heat storage material is selected from the group consisting of: cast iron, aluminum and mixtures thereof
In one embodiment of the present invention, the magnetic material has holes or slits therethrough and panels of the heat storage material are disposed in the holes or slits.
In a further embodiment of the invention, the means for generating induction energy comprises at least one energizing portion having a means for inducing magnetic field; and a means for converting current between alternating current and direct current. Preferably, the means for converting current between alternating current and direct current, converts alternating current at a given frequency to direct current, then reconverts to alternating current at a much higher frequency. In one embodiment of the invention, an inverter is the means for converting current between alternating current and direct current. In another embodiment of the invention, the means for inducing magnetic field is at least one inductive coil.
In an embodiment of the invention the means for generating induction energy further comprises a means for controlling the inverter; an air inlet aperture; a fan; a position sensor; and an electromagnetic interference filter. The induction power source comprises an inverter connected to at least one inductive or magnetic coil which is capable of producing a magnetic or electric field that energizes the magnetic particles of the heat storage member until its predetermined power percentage is reached.
The present invention also provides a system for heating food delivery containers which comprises: at least one container for delivering heated food which comprises a food compartment having at least one self-regulating heat storage member disposed therein, wherein the self-regulating heat storage member comprising a magnetic material; and a means for generating induction energy which is capable of heating the magnetic material to a predetermined temperature, wherein the means for generating induction energy provides induction energy to one or more containers.
In one embodiment of the invention, the means for generating induction energy comprises at least two energizing portions; wherein said at least two energizing portions share a means for inducing magnetic field and a means for converting current between alternating current and direct current. The means for inducing magnetic field is at least one inductive coil and the means for converting current between alternating current and direct current is an inverter. In another embodiment of the invention, the inverter divides its power supply between the energizing portions when the containers are disposed on the energizing portions.
The present invention further provides a method of heating a food delivery container which comprises: (a) placing a container about an induction generating means, the container comprising at least one food compartment having at least one self-regulating heat storage member disposed therein; (b) activating the induction generating means to heat the heat storage member to a predetermined temperature; and (c) deactivating the induction generating means once the heat storage member reaches the predetermined temperature. In an embodiment of the invention, the deactivation step occurs automatically at the predetermined temperature. In another embodiment of the invention, the activation step repeats automatically after a set period of time if the container remains disposed on the induction generating means.
The present invention also includes a food delivery container having a fail-safe feature that prevents the food delivery container from over-heating, and thus provides a novel safety feature for food delivery containers, particularly pizza delivery containers.
Further objects and features of the present invention will be apparent from a review of the following specification including the drawings, wherein key features have been given like numbers.